Process for pest control



Patented Jame 4, 1929.

UNITED STAT that RALPH M. JACKSON, OF LA HABRA, CALIFORNIA, ASSIGNOR 0FONE-HALF TO GALE FORNIA CYANIDE COMPANY, A CORPORATION OF DELAWARE,

PROCESS FOR PEST CONTROL.

No Drawing.

My invention relates to the fumigation of trees for pest control, andmore-particularly to fumigation by a highly volatile gas introducedbeneath a tent covering a tree.

It is the object of the invention to elimi nate the laborious,inconvenient, and disagreeable work incident to the original pot methodof fumigation, and also obtain increased insecticide efliciency over thepresent method of applying a dose of gas in one volume.

In the original pot method of fumigation, an insecticide gas was formedby fuming chemicals in a pot placed beneath a tree which was coveredwith a tent, it being found by experience that best results wereobtained when the tents were left on the trees for approximately onehour. I v

By thepot method the gas was not released suddenly in one volume, butwas maintained for a considerable length of time 'at a mean insecticidegas concentration by the continuous fuming of the chemicals. As a consequence there was no excessive leakage from the tents due-to extremelyhigh gas concentration, and the continuous fuming constantly replacedthe relatively slow leakage of gas in order to maintain a meaninsecticide con- Very satisfactory results were obtained by thisprocess, slnce there was never centration.

such excessive concentration of the gas as would be liable to injure thetrees or fruit under normal conditions, and the mean insecticide gasconcentration was maintained for a suflicient length of time toeffectively destroy pests on the trees.

It was onl the inconvenience of the pot method that lied to the adoptionof the applicator method of fumigating, which consists of discharging adose of insecticide gas in one volume beneath a tent covering a tree.The sudden full volume of gas is introduced beheath a tent from' amechanical applicator discharging a liquid concentrate previouslymanufactured from suitable chemicals.- The dosage originall used in thismethod. was based upon the dosage previously found efficient under thepot method, and the time of egposure was the same, but the insecticide eciency frequently did not average nearly as high.

The subject has received considerable study, but entomologists andscientists have Application filed July 15, 1925. Serial No. 43,845.

failed to account for this loss in efliciency, and the remedies proposedhave proved unsatisfactory and inadequate. An increase in the dosage hasaccomplished slightly better the increased injury to trees and fruit hasproved a serious detriment until the discovcry of the causes, which hasresulted in the present improved fumigating process.

- By experiments and comparisons of the pot and applicator methods, Ihave determined that the superior efficiency of the pot method as aninsecticide, results from maintaining a mean' gas concentration for arelatively" long time, without excessively high concen tration at thebeginning of the operation, or

, subsequent rapid decline below minimum insecticide efficiency. As aconsequence the gas concentration is never sufiiciently high undernormal conditions to cause injury to the-trees or fruit, but, on theother hand, the gas concentration' remains above minimum insecticideefficiency for a sulficientlength of time to complete the destruction ofthe pests.

.1 have also determined that the uhsatis factory-results obtained by theapplicator method are due to the high initial gas concentrationresulting from the release of the dose in one volume. The proportion ofgas leaking from a tent increases rapidly as the concentration of thegas is increased, and this is particularly true when the tents are dryand there is not an excess of humidity, conditions which unfortunatelyare otherwise most favorable for efiicient fumigation, and

as a consequence the initial high gas concentration under the applicatormethod rapidly leaks from the tents and quickly declines be- -lowminimum insecticide efiiciency, so that an efficient insecticideconcentration of the gas is not maintained for a sufficient length oftime to effectively destroy the pests.

If the initial high gas concentration is increased by an increase in thedosage, a concentration above minimum insecticide efii ciency is ofcourse maintained for a same what longer time, but the increase in theperiod of insecticide efficiency is seriously curits tailed by the rapidincrease in the leakage of gas at the higher concentration. As aconsequence if concentration at insecticide eificlency is to bemamtame'd for a SlllfiClGIlt;

I vented a process 0 fumigation combining tion of fumi l of time or oter waste. ill!v the advantages of the pot and applicator I methods andwithout the disadvantages thereof. The insecticide gas is dischargedunder a tent from an applicator, thereby eliminating the inconveniencesof the pot method, and

the gas is applied in suchdoses and at such intervals of time as tomaintain a gas concentration of mean insecticide efliciencfor asuflicient period of time to efiectively estroy the pests, and withoutan excessive initial gas concentration. p

' The impr' ved process which thus provides maximum'insectici'de'efficiency, is also adapted for use without an increase inthec'onsumpating material, and with no loss Referring to my process indetail, a dose of the fumigant which may be approximately equal to thatheretofore discharged under a tent in one volume, is' divided into-aplurality of doses which are successively discharged under a tentat'predetermined intervals oftime. The part'of the dose which isinitially alpplied, hereinafter referred to as'the first 0t, issuflicient to produce a gas concentration of mean insecticideefliciency, but not' suflicientlyhigh as to injure the trees or fruit orcause. excessive leakage from the tent. There is of course-some leakageof the gas so that the gas concentration is gradually re= -duoed, but.the initial concentration being of mean insecticide efliciency, it willbe some time-before the'gas concentration declines to insecticideefliciency, and before this point isreached another part of the fulldos'e,'h ereinafter referred to as. the second shot, is dischargedbeneath thetent, This".

'- 1 second shot is for the purpose of again establishing approximately.the original gas con- .centration, so that as the gas again graduallflescapes, mean insecticide concentration wi be vagain maintained for anappreciable length of time, without excessive initial concentration oran excessively'rapid'. decline in gasconcentration.

From ex riments with this method I have determine that by not employingan fixcesf Application'of a full dose in sive initial gas concentration,leakage of gas from the tents may be reduced to approximately 33 92; foreach ten minutes .of exposure, so that,a continuous gas concentration ofmean insecticide 'eiiiciencymay be maintained, for a suilicient lengthof time to effectively destroy pests, by dividing the orig inal dose offuinigant into two shots and applylng the same at approximately twentyminute intervals,"the first sh0t-,being from 30% to 50% greater than thesecond shot,

since at the time the latteris applied, there is still a gasconcentration under the tent in excess of minimum insecticide eficiency,and the purpose of the second shot is simply to reestablishapproximately the original con centration. a J

two shots as thus. described, also permits ofpractical op-. eration-inan orchard without Waste of time and at maximum operating efliciency,when workinggwith approximately sixty tents as Is the usual practice; 7'

.':-A supply stationispreferably located near the center of-jthe stringof approximately sixty trees-covered'-' with tents, and the 0peratorswork from-this station ,and return to it when each half of thestringoftrees has been fumigated; 1

Two applicators of desired mechanical constructlon and the'accompanyingpperators workrom the supply station and successively .areemployed fdr milking the first and sec- 0nd; shots respective] The firstshooter, followln' the taper an tent pullers, starts the,

applies the first'shot to the trees of one-half of A the string. 'Thenormal full dosage having been previously determined in accordancewith-thecondition of the trees and climatic conditions as is the usualpractice, and the proper ratio between the first and second shots havingalso been decided, the dosage applied to each tree by the first shot, iscomputed -by the measurements of the respective trees with relation tothe basic dosage, and

the firstshootercharts the-dosage on-a first chart as he progresses tothe end of the string. He then returns to the supply station and turnsover the first chart to the second shooter,

the elapsed time closely approximating the desired interval between thetwo shots. The second shooter then applies the second shot to succeedingtrees of the'first half of the string, basing the dosage upon thedesired ratio bhtween the second shot and the applied dosage of thefirst shot as indicated upon the chart which he has received.

When he reaches the endof the string the I second shooter. returns tothe supply station, and in the meantime the'first shooter hasapplied'the first shot to the other half- .of 'the string of'trees andhas'returned' to the supply station where he turns "over to the secondshooter a second chart showing the dosagewhich he has appliedtothesecond half of the string of trees. The second shooter then appliesthe second shot to the second half f the string, using the second chartto de- .termine .the dosage, and while the second shooter is finishingthe Work on the second half of the string .of trees, the first shooterhas moved on and completed the first shot on one-half of the trees ofthe next string. The work thus progresses without delay, and with thesucceeding shots applied at such an interval as to maintain a gasconcentration in excess of minimum insecticide efficiency for acomparatively long period of time.

I am aware that so called double shooting has been heretofore tried,under which method a full dosage is applied in one volume, and afterexposure for the normal period employed for a full shot, the operationis repeated. As a consequence theinitial gas concentration is excessive,and deteriorates below minimum insecticide efl'iciency long before thesecond full shot is applied, thereby allowing the pests to recoverbefore subjecting the same to the second dose. The second shot thereforedoes not continue a gas concentration of unbroken mean insecticide efiiciency as established by the first shot. 4 By my improved method, on theother hand, only one fulldose is necessary,'and

the gas concentration is never excessive but continues for a relativelylong time at mean insecticide e'liiciency so as to ofi'er no opportunityfor recovery of the pests.

I claim:

-1. The process of 1 treating trees with a volatile fumigant for pestcontrol which consists of-making a plurality of doses'of thefumigant atsuch intervals of time hearing such relation to the relative strength ofthe respective applications as to maintain a con tinuous gasconcentration above minimum insecticide efliciency throughout andoverlapping the intervals of time between the successive applications ofthefumigant and destroy the pests.

2. The process of treating trees with a volatile fumigant forpest'control which consists of making such van application of thefumigant as to produce a gas concentration which is below tree injuringconcentration but is adapted to maintain a gas concentration aboveminimum insecticide efiiciency for an appreciable period, and makingsuch for a suiiicient length of time to effectively a second applicationof the fumigant just prior to the end of said period as to reestablishgas concentration which is below'tree in-,

juring concentration and continue gas concentration above minimuminsecticide cfficiency for another appreciable period.

3. The process of treating trees with a volatile fumigant for pestcontrol which consists of making such an application of the fumigant asto produce a gas concentration which is below tree lIlJllIlIlgconcentration but is adapted to maintain'agas concentration aboveminimum insecticide efficiency for ap proximately one-half the period ofexposure necessary for efiective'destruction of pests,

and making such a second application of the lish approximately theoriginal-gas concentration and continue gas concentration in excess ofminimuminsecticideefliciency for the remainder of the periodnecessaryfor effective pest destruction. 1 j

4. The process of treating trees with a volatile fumigant for pestcontrolwhich consists of making initial. application of the treescovered with tents, and after reaching the endof the string immediatelymaking second applications of the fumigant to the,

succeeding trees, the number of trees treated '70 fumigant before theexpiration of said first half ofthe period ofexposui'e, as to reestab--in the string being such as to provide a time interval between therespective applications which bears suchrelation to thev relativestrength of the applications that said applications will cooperate tomaintain a continuous gas concentration which 1s never of such tervaland for'aosufficient length of time to effectively destroy pests.

- excessive concentration asto injure the trees, but which-1s abovemlnlmum msecticide eiii ciencythroughout and beyond said time -in-- 5.The process of" treating trees with volatile fumigant forlpest controlwhich consists of successively making an initial appli cation of the'fumigan t to therespective trees in accordance with themeasurementsthereof, charting the initial application applied to the respectivetrees,: and after making the initial application to the'respective treesimmediately making a second application of the fumigant tosaidsuccessive trees, said second application being computed as aproportional part of the initial application indicated by I saidcharting, the respective applications and the elapsed time between themaking thereof being such as to maintain acontinuous gas concentrationwhich is7 never of such excessive concentration as to injure the treesbut which is above minimum insecticide 'eficiency throughout and beyondsaid elapsed time and for a suiiicient length of time to ef-.

fectively destroy pests.

6. The process of treating trees with a- 80 fumigant. to succeedingtrees of a string of cliately starting from the center of the string andmaking the second application of the fumigant to succeeding treescof thesecond half of the string, the relative applications.

5 hearing such relation to theelapsed time betrees but which is inexcess of minimum insecticide efliciencythroughout and beyond 10 saidelapsed time and for h suflicient length of time to effectively destroypests.

In testimony whereof I hereunta afiix my I signature.

RALPH M. JACKSON.

